Conventionally, various image display apparatuses such as a liquid crystal display apparatus, a PDP [Plasma Display Panel] and the like are proposed. Generally, an image display apparatus is provided with a light emitting device for image display that emits light which is used for image display. The image display apparatus suitably controls light transmittance and light intensity based on given image data, thereby displaying an image.
For example, a liquid crystal display apparatus includes a backlight unit (which corresponds to a portion of the above light emitting device for image display) and a liquid crystal panel; to display an image, light transmittance of the backlight unit is controlled by the liquid crystal panel. Besides, as such backlight unit, various types are devised.
As an example, a backlight is devised, in which a plate-shaped member disposed to oppose a liquid crystal panel is divided in a plurality of areas (regions) and light emitting elements are disposed on each area. Besides, further, a patent document 1 discloses a type of backlight unit (hereinafter, sometimes called an “area drive type” for the sake of convenience), in which light emitted from light emitting elements disposed in each area is controlled for each area.
According to the image display apparatus disclosed in the patent document 1, brightness of backlight (i.e., light emission power supplied to the light emitting element of the backlight unit) is adjustable for each area based on image data (i.e., the brighter a corresponding image portion is, the brighter light the light emitting element belonging to the area is made to emit), and an image having a high contrast ratio is obtainable.
Here, as the light emitting element, an element, typically, an LED [Light Emitting Diode], which emits light in accordance with a supplied current (brightness of the emitted light changes), is the most common. Besides, consumed power of a backlight unit using such a light emitting element nearly depends on a sum of currents flowing (supplied) in respective light emitting elements when a voltage applied to the light emitting element during a time of light emission is constant.